335 research outputs found
SEARCH FOR NEUTRINO OSCILLATION AT BUGEY
The high flux of low energy [MATH]e produced by the core of a PWR reactor of Bugey power plant has been used to search for evidence of neutrino oscillations through the inverse beta decay reaction [MATH]e + p → e+ + n. Measurements have been performed at two distances (13.5 and 18.5m). About 50 000 [MATH]e events have been collected at the first position and 25 000 [MATH]e events at the second one. Data analysis is almost completed
Extrinsic CPT Violation in Neutrino Oscillations in Matter
We investigate matter-induced (or extrinsic) CPT violation effects in
neutrino oscillations in matter. Especially, we present approximate analytical
formulas for the CPT-violating probability differences for three flavor
neutrino oscillations in matter with an arbitrary matter density profile. Note
that we assume that the CPT invariance theorem holds, which means that the CPT
violation effects arise entirely because of the presence of matter. As special
cases of matter density profiles, we consider constant and step-function matter
density profiles, which are relevant for neutrino oscillation physics in
accelerator and reactor long baseline experiments as well as neutrino
factories. Finally, the implications of extrinsic CPT violation on neutrino
oscillations in matter for several past, present, and future long baseline
experiments are estimated.Comment: 47 pages, 7 figures, RevTeX4. Final version to be published in Phys.
Rev.
Interpreting Reactor Antineutrino Anomalies with STEREO data
Anomalies in past neutrino measurements have led to the discovery that theseparticles have non-zero mass and oscillate between their three flavors whenthey propagate. In the 2010's, similar anomalies observed in the antineutrinospectra emitted by nuclear reactors have triggered the hypothesis of theexistence of a supplementary neutrino state that would be sterile i.e. notinteracting via the weak interaction. The STEREO experiment was designed tostudy this scientific case that would potentially extend the Standard Model ofParticle Physics. Here we present a complete study based on our full set ofdata with significantly improved sensitivity. Installed at the ILL (InstitutLaue Langevin) research reactor, STEREO has accurately measured theantineutrino energy spectrum associated to the fission of 235U. Thismeasurement confirms the anomalies whereas, thanks to the segmentation of theSTEREO detector and its very short mean distance to the core (10~m), the samedata reject the hypothesis of a light sterile neutrino. Such a directmeasurement of the antineutrino energy spectrum suggests instead that biases inthe nuclear experimental data used for the predictions are at the origin of theanomalies. Our result supports the neutrino content of the Standard Model andestablishes a new reference for the 235U antineutrino energy spectrum. Weanticipate that this result will allow to progress towards finer tests of thefundamental properties of neutrinos but also to benchmark models and nucleardata of interest for reactor physics and for observations of astrophysical orgeo-neutrinos.<br
Interpreting Reactor Antineutrino Anomalies with STEREO data
Anomalies in past neutrino measurements have led to the discovery that these
particles have non-zero mass and oscillate between their three flavors when
they propagate. In the 2010's, similar anomalies observed in the antineutrino
spectra emitted by nuclear reactors have triggered the hypothesis of the
existence of a supplementary neutrino state that would be sterile i.e. not
interacting via the weak interaction. The STEREO experiment was designed to
study this scientific case that would potentially extend the Standard Model of
Particle Physics. Here we present a complete study based on our full set of
data with significantly improved sensitivity. Installed at the ILL (Institut
Laue Langevin) research reactor, STEREO has accurately measured the
antineutrino energy spectrum associated to the fission of 235U. This
measurement confirms the anomalies whereas, thanks to the segmentation of the
STEREO detector and its very short mean distance to the core (10~m), the same
data reject the hypothesis of a light sterile neutrino. Such a direct
measurement of the antineutrino energy spectrum suggests instead that biases in
the nuclear experimental data used for the predictions are at the origin of the
anomalies. Our result supports the neutrino content of the Standard Model and
establishes a new reference for the 235U antineutrino energy spectrum. We
anticipate that this result will allow to progress towards finer tests of the
fundamental properties of neutrinos but also to benchmark models and nuclear
data of interest for reactor physics and for observations of astrophysical or
geo-neutrinos.Comment: 21 pages, 13 figure
Determination of the muon charge sign with the dipolar spectrometers of the OPERA experiment
The OPERA long-baseline neutrino-oscillation experiment has observed the
direct appearance of in the CNGS beam. Two large muon
magnetic spectrometers are used to identify muons produced in the
leptonic decay and in interactions by measuring their charge and
momentum. Besides the kinematic analysis of the decays, background
resulting from the decay of charmed particles produced in
interactions is reduced by efficiently identifying the muon track. A new method
for the charge sign determination has been applied, via a weighted angular
matching of the straight track-segments reconstructed in the different parts of
the dipole magnets. Results obtained for Monte Carlo and real data are
presented. Comparison with a method where no matching is used shows a
significant reduction of up to 40\% of the fraction of wrongly determined
charges.Comment: 10 pages. Improvements in the tex
Observation of nu_tau appearance in the CNGS beam with the OPERA experiment
The OPERA experiment is searching for nu_mu -> nu_tau oscillations in
appearance mode i.e. via the direct detection of tau leptons in nu_tau charged
current interactions. The evidence of nu_mu -> nu_tau appearance has been
previously reported with three nu_tau candidate events using a sub-sample of
data from the 2008-2012 runs. We report here a fourth nu_tau candidate event,
with the tau decaying into a hadron, found after adding the 2012 run events
without any muon in the final state to the data sample. Given the number of
analysed events and the low background, nu_mu -> nu_tau oscillations are
established with a significance of 4.2sigma.Comment: Submitted to Progress of Theoretical and Experimental Physics (PTEP
Limits on muon-neutrino to tau-neutrino oscillations induced by a sterile neutrino state obtained by OPERA at the CNGS beam
The OPERA experiment, exposed to the CERN to Gran Sasso beam,
collected data from 2008 to 2012. Four oscillated Charged Current
interaction candidates have been detected in appearance mode, which are
consistent with oscillations at the atmospheric within the "standard" three-neutrino framework. In this paper, the OPERA
appearance results are used to derive limits on the mixing
parameters of a massive sterile neutrino.Comment: 11 pages, 4 figures; reference to Planck result updated in the
Introduction. Submitted to JHE
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